The organic chemical hydride process for hydrogenating aromatic compounds such as toluene has recently been developed for the purposes of storing and transporting hydrogen in the form of hydrogenated aromatic compounds (or organic hydrides). According to this process, hydrogen is converted into a hydrogenated aromatic compound at the site of production, and transported in the form of the hydrogenated aromatic compound. The hydrogenated aromatic compound is separated into the hydrogen and the aromatic compound at a plant or a hydrogen station located near a city or other user of hydrogen by dehydrogenating the hydrogenated aromatic compound. The aromatic compound produced from this dehydrogenation process is transported back to the production site of hydrogen to be hydrogenated by hydrogen once again.
It is known that the catalyst used for the dehydrogenation process is degraded over time by a poisoning substance contained in the hydrogenated aromatic compound (impurities contained in the aromatic compound before being hydrogenated, or impurities produced during the hydrogenation process), and has a limited service life. The kind and the amount of the poisoning substance vary depending on the reaction condition of the hydrogenation process, but most of such substances have higher boiling points than the boiling point of the hydrogenated aromatic compound.
It is also known in a hydrogen storage and transportation system based on the organic chemical hydride process to maintain the concentration of the poisoning substance that is mixed with the hydrogenated aromatic compound (such as methylcyclohexane) in the product of the hydrogenation process by providing a distillation unit following the hydrogenation reaction unit to remove the poisoning substance from the dehydrogenation catalyst and extend the service life of the catalyst. See Patent Document 1.